Metal-Metal Friction Characteristics and Gear Pitting Life Performance of Metal V-Belt type CVTFs

摘要

There is an increasing number of passenger cars that are equipped with metal V-belt type continuously variable transmissions (B-CVTs). The performance requirement of lubricants for B-CVTs (CVTFs) should be focused on achieving a higher metal-metal friction coefficient and guaranteeing gear pitting life in the CVT units. This study intends to clarify lubricant additive effects on these performances of B-CVTs. The friction characteristics between the metals were evaluated by using a block-on-ring type tribometer (Falex LFW-1), the gear pitting life was tested by using standard FZG gear test rig. As a result, an additive formulation consisting of extreme pressure agent, calcium detergent and dispersant showed a higher friction coefficient between the metals. The results of the surface analysis indicate a substrate, presumed to be calcium compounds, formed small islands. Because this tribofilm is rougher, it is assumed there is a higher friction coefficient. Moreover, it is found that a sort of extreme pressure agent gives a longer fatigue life with keeping higher metal-metal friction coefficient.